RFC 3428 (rfc3428) - Page 2 of 18


Session Initiation Protocol (SIP) Extension for Instant Messaging



Alternative Format: Original Text Document

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RFC 3428                 SIP Message Extension             December 2002


Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY" and "OPTIONAL" are to be interpreted as described
   in BCP 14, RFC 2119 [6] and indicate requirement levels for compliant
   SIP implementations.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.    Scope of Applicability . . . . . . . . . . . . . . . . . . .  3
   3.    Overview of Operation  . . . . . . . . . . . . . . . . . . .  4
   4.    UAC Processing . . . . . . . . . . . . . . . . . . . . . . .  5
   5.    Use of Instant Message URIs  . . . . . . . . . . . . . . . .  6
   6.    Proxy Processing . . . . . . . . . . . . . . . . . . . . . .  6
   7.    UAS Processing . . . . . . . . . . . . . . . . . . . . . . .  7
   8.    Congestion Control . . . . . . . . . . . . . . . . . . . . .  8
   9.    Method Definition  . . . . . . . . . . . . . . . . . . . . .  9
   10.   Example Messages . . . . . . . . . . . . . . . . . . . . . . 11
   11.   Security Considerations  . . . . . . . . . . . . . . . . . . 13
   11.1  Outbound authentication  . . . . . . . . . . . . . . . . . . 13
   11.2  SIPS URIs  . . . . . . . . . . . . . . . . . . . . . . . . . 14
   11.3  End-to-End Protection  . . . . . . . . . . . . . . . . . . . 14
   11.4  Replay Prevention  . . . . . . . . . . . . . . . . . . . . . 14
   11.5  Using message/cpim bodies  . . . . . . . . . . . . . . . . . 15
   12.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 15
   13.   Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
   14.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 15
   15.   Normative References . . . . . . . . . . . . . . . . . . . . 16
   16.   Informational References . . . . . . . . . . . . . . . . . . 16
   17.   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 17
   18.   Full Copyright Statement . . . . . . . . . . . . . . . . . . 18

1. Introduction

   Instant Messaging (IM) is defined as the exchange of content between
   a set of participants in near real time.  Generally, the content is
   short text messages, although that need not be the case.  Generally,
   the messages that are exchanged are not stored, but this also need
   not be the case.  IM differs from email in common usage in that
   instant messages are usually grouped together into brief live
   conversations, consisting of numerous small messages sent back and
   forth.

   Instant messaging as a service has been in existence within intranets
   and IP networks for quite some time.  Early implementations include
   zephyr [11], the UNIX talk application, and IRC.  More recently, IM



Campbell, et. al.           Standards Track


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